You use a common Office 2010 installation with the PDF editing tool Foxit Phantom 2.2.x. When you copy some text to the clipboard and then start Word, the clipboard is suddenly empty.
The Foxit Phantom PDF Suite installation comes with a Word Add-In which is not really useful in my opinion (Word can create PDF files itself). Anyway, if Word is loaded with this Add-In, the clipboard content is deleted on its startup.
If you use only 1 PC, you can deactivate the add-in in the common Word options -> Add-Ins -> Go to COM Add-ins -> Uncheck the Foxit Add-In.
If you are in a domain with multiple workstations, it may be useful to open your GPO and add a registry element under Computer Configuration.
The element LoadBehavior, which you have to change to Hex “2”, is located in HKLMSOFTWAREWow6432NodeMicrosoftOfficeWordAddinsFPC_WordAddin.FpcWordAddin.
After the workstations’ next reboot, the Add-In should not be loaded any more. To be sure, check the list of enabled Add-Ins in Word options again.